A parasitic worm is emerging as a potent weapon against one of Australia's most resilient pests - the cane toad. The toxic amphibians have spread across the country since they were introduced into Queensland in the 1930s in an attempt to combat the cane beetle. As Phil Mercer in Sydney reports, tens of millions of dollars have been spent over the years to keep the nation's ugliest pest at bay.

As many as 100 million cane toads are spread across tropical northern Australia.

The toads were introduced to the northern Australian state of Queensland from Hawaii in 1935 to eradicate cane beetles, which were destroying sugar cane crops.

The experiment failed. But the cane toad has succeeded in spreading across a country where it has few enemies, and it has caused massive environmental damage.

The toxic pests eat other frogs as well as small reptiles, birds and mammals. Crocodiles and dingoes have also died after eating their poisonous skins.

But Australian scientists are celebrating a big step forward in the fight against the cane toad.

Professor Rick Shine from Sydney University's School of Biological Science says that a parasitic worm could be a powerful weapon against the marauder.

"There's a small parasite that occurs in Australian frogs in Queensland, and it's moved across to the cane toad, and the research is showing that it kills baby toads in fantastic numbers and the ones that survive grow slowly and can't move so well," he said. "And we're hopeful that it may offer a real breakthrough as an opportunity for controlling cane toad populations.

So far the lungworm parasite has only been found in cane toad populations in Queensland.

Researchers hope to introduce it in other areas to stop the toads' advance through the Northern Territory and into Western Australia.

There is no broad agreement as to the best way to control toad numbers.

One Australian politician sparked outrage when he suggested that residents should beat cane toads to death with golf clubs or cricket bats.

Animal welfare groups have promoted what they consider a more humane method. They advise placing toads in a freezer until they die.

Earlier this year a giant cane toad the size of a small dog and nicknamed Toadzilla was captured in northern Australia.

Toadzilla was the biggest cane toad ever found in the Northern Territory and weighed about a kilogram.